Sheet pack opener mechanism



Aug. 2, 1955 o. J. s IMLER ET AL SHEET PACK OPENER MECHANISM 5 SheetsSheet 1 Filed Jan. 20, 1951 Ira/627212725 fiagpkcjaunzler' and Aug. 2, 1955 o. J. SIMLER ET AL 2,714,241

SHEET PACK OPENER MECHANISM Filed Jan. 20, 1951 5 Sheets-Sheet 2 W/A f nz/enZ 715',

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SHEET PACK OPENER MECHANISM Filed Jan. 20, 1951 5 Sheets-Sheet 4 fnveniors" a by ficzp/. Cfic'zunier and Aug. 2, 1955 0, J, LE ET AL SHEET PACK OPENER MECHANISM 5 Sheets-Sheet 5 Eiled Jan. 20, 1951 E7" and nited tates atent O SHEET PACK OPENER MECHANISM Oscar J. Simler, Sebring, and Ralph C. Saunier, Canton, Ohio, assignors to Borg-Warner Corporation, Chicago, HL, a corporation of Illinois Application January 20, 1951, Serial No. 206,958

12 Claims. (Cl. 29-17) The present invention relates to machines for opening packs of sheets, and particularly metal sheets in laminated packs, but may be used for opening sheets of packs of various materials where the sheets are compressed together in a body and firmly adhere to one another.

The principal object of the present invention is to provide an apparatus for separating packs of sheets which will enable the packs to be rapidly broken up and the individual sheets separated therefrom with the least possible damage to the sheets.

In the manufacture of thin metal sheets by the pack rolling process, it is substantially impossible to prevent the sheets in the pack from rigidly adhering to each other. The extent of this adherence is quite variable, depending to a great extent on the composition of the steel or other metal and the regulation of the heat treatments to which the pack is subjected during the rolling process. When operating conditions are at their best, a considerable number of the rolled packs will be firmly stuck together. These packs, in which the sheets are firmly stuck together, are called stickers and sometimes are stuck together to the extent of being welded. The method in use generally at the present time for separating the stickers is a hand operation, in which one man breaks open the corners of the pack so that he can grasp an individual sheet with a pair of tongs. If the sheets are not too large, he can then tear the individual sheet from the remainder of the pack, however, with this method of operation the corner of the sheet which is grasped by the tongs is very often mutilated to such an extent that the end of the sheet must be cut off. If the sheets are relatively large it requires considerable effort to separate one of them from the pack. In this case the corner of the sheet is held from the pack by one man by means of tongs or a hook or some similar instrument and another man, while using a long heavy knife or sword, beats the sheet from the remainder of the pack. Quite generally when this method of separating the sheets is used there is a large amount of waste as the sword frequently pierces or tears one or the other of the adherent sheets.

It is thus another object of the present invention to separate sheets from a pack with a minimum of waste, time and effort.

In the present invention the packs are advanced through a device which initially flexes them to thereby partially separate all of the sheets of the pack. The pack is then successively advanced through a group of stripping devices, each one of which strips an individual sheet completely from the pack and deposits it upon a conveyor.

Another object of the invention is thus to provide a device for initially flexing a pack of metal sheets to partially separate the sheets of the pack without damaging them in any way. In connection with this object of the invention, the flexing device comprises two rotatable members, each of which has an equal number of individually rotatable planetary rollers. In operation the rotatable members are positioned above and below a 2,714,241 Patented Aug. 2, 1955 pack and the pack advanced therebetween. The individual planetary rollers of each of the rotatable members mesh slightly and as the rotatable members are rotated, the, pack is successively flexed in opposite directions which tends to break up the pack. After the pack has been flexed sufficiently it is advanced through the stripping devices.

Each of the stripping devices has a pivotal member provided with a serrated, knurled or toothed surface, for frictionally engaging the lowermost sheet of the pack. As the pack is advanced through one of the stripping devices it moves the pivotal member in an arc and due to the movement of the pack and the are traced by the pivotal member, the leading edge of the lowermost sheet is peeled from the remainder of the pack. It is thus another object of the present invention to provide a stripping device including a pivotal member having a frictional surface thereon for initially peeling the leading edge of the lowermost sheet in a pack as the pack is advanced through the stripping device.

The pivotal member, besides being effective to peel the lowermost sheet from the pack during the advance of the pack through the stripping device, also directs the peeled lowermost sheet between a pair of pinch rollers which subsequently advance the sheet onto a conveyor. After the pivotal member has peeled the leading edge of the lowermost sheet from the pack, a knife is moved between the lowermost sheet and the remainder of the pack, which, during the subsequent advance of the pack, completely strips the lowermost sheet therefrom. Means are provided for reciprocating the knife to thereby facilitate the stripping of the lowermost sheet as it is advanced through the stripping device.

It is therefore another object of the present invention to provide a stripping device wherein a pivotally mounted friction engaging means peels the leading end of a sheet from a pack and a reciprocable knife thereafter completely strips the sheet from the remainder of the pack.

A further object of the invention is to provide a stripping device wherein a pivotal member strips the leading edge of a sheet from a pack and controls the movement of a knife into a position between the partially stripped sheet and the remainder of the pack during advance thereof through the stripping device.

Another object of the invention is to provide a pack stripping device having means for peeling the leading edge of one sheet from a pack, such means being effective to cause a knife to be moved into a position between the partially stripped sheet and the remainder of the pack in order to enable the knife to completely strip the sheet from the pack during subsequent advance thereof, and also including a sensing means for sensing the pack and effective upon the passage of the pack beyond the sensing means to return the knife to its initial position.

Another object of the invention is to provide a stripping device wherein a pivotally mounted member having a friction surface thereon for engaging one sheet of the pack is effective to initially strip the leading edge of the one sheet from the pack and upon such initial stripping is further effective to cause a knife to be moved into a position whereby the partially stripped sheet is completely stripped from the pack during subsequent advance thereof, the stripping device also including a pack sensing means for causing the return of the knife and the pivotal member to their initial positions after the passage of the pack beyond the sensing means.

The above and other objects and advantages of the present invention will become apparent and the invention will be more readily understood from the following 3 detailed description when read in conjunction with the accompanying drawings in which:

Fig. 1 is a general view of the invention;

Fig. 2 shows the device for. initially .partially breaking upapack;

Fig. 3 is an end view of one of the stripping devices taken substantially along the line 33 in. Fig. 1;

Fig. 4 is a side view of oneof the stripping devices showing the pack in theposition in whichit firstengages the pivotally mounted friction member;

Fig. 5 is a side view of one of the stripping devices showingthe knife in stripping position'between the lowermost sheet and the remainder vof the. pack;

Fig. 6 is a detailed view of themechanisrn for returning the pivotal friction members to their initial position preparatory to theadvance of a second pack through the stripping device; and.

Fig. 7 is a detailed view of the knife used in the stripping devices.

Referring now to the drawings, wherein like reference numerals designate identical parts throughout the drawings, and more particularly to Fig. l, a base 10 is provided which has a plurality of stripping devices 11 mounted thereon. A device indicated generally by reference numeral 12 is provided for initially flexing the pack in order to partially break up the sheets therein prior to the passage of the pack through the different stripping devices. A suitable conveyor 13, shown in Fig. 1 as a belt, is provided for receiving the sheets as they are stripped from the pack by the stripping devices 11.

With reference particularly to Fig. 2 the flexing device 12 is provided with two sets of pinch rolls 14, carried by suitable brackets, for advancing the pack through the flexing device. Each of the pinch rolls 14 comprises a rotatable roller 15 which is power-driven-for advancing the pack, and a vertically reciprocable rotatable roller 16. Each of the rollers 16 is spring pressed downwardly by a suitable compression spring 17. The springs 17 retain the rollers 15 and 16 engaged with the packv with sulTrcient-force to prevent slippage of thepack relative to the rollers as it is advanced therebetween. A freely rotatable roller 13 is suitably mounted in the frame of the flexing-device for supporting the pack prior to its entrance into the pinch rolls 14.

The flexing device 12 includes a pair of rotatable members 19 and 20. The rotatable member 19 is mounted on a. shaft 21 and the rotatable member 20 is mounted on a shaft 22, each of the shafts being power driven. Secured respectively to the shafts 21 and 22 are plates 23 which roughly assume the shape of a clover-leaf. Four freely rotatable planetary rollers 24 are freely rotatable about shafts 25 secured to the plates 23 and 24. A cylinder 26 having a piston 27 reciprocable thereinis provided for raising and lowering the rotatable member 20. It is contemplated that the piston.27 will be moved either up or down by air or some other fluid under-pressure. It is further contemplated that suitable means will be provided for admitting the fluid-above the piston in order to force the rotatable member 20 downwards and that other suitable means will be provided for admitting fluid into the cylinder 26 below thepiston 27 in order to raise the rotatable member 20.

The rotation of the pinch rolls 14 may .be controlled in order to advance the pack into a position between the two rotatable devices 19 and 20 and then stop the pack in such position. Means are also provided for controlling the rotation of the rotatable members 19 and 20. After the pack is advanced into a position between the rotatable members 19 and 2t the'shafts 21 and 22 are rotated in opposite directions. It is apparent from Fig. 2.that although the rollers. 24 of each rotatable member 19 and 20 do not engage one another, they nevertheless overlap somewhat or mesh without touching each other duringthe rotation of the members 19 and 20. When the member 19 rotates counterclockwise andthe member 20 rotates clockwise with a pack positioned therebetween, one of the rollers 24 in the rotatable member 19 will first tend to raise the pack whereas a roller 24 of the member 20 will tend to lower the pack. The resulting effect of the rollers 24 on the pack is to flex it first upwardly and then downwardly which causes at least a partial separation of the sheets in the pack. After'the pack has been flexed sufficiently by the flexing device 12, the rotation of the members 19 and 20 is stopped and the pinch rolls 14 are again rotated to advance the pack into the first stripping device 11.

Each of the stripping devices 11 is provided with side walls 37 to which are secured suitable bushings 38 for rotatably supporting a shaft 39. The side wall 37 (at the right in Fig. 3) is provided with an aperture through which the shaft 39 protrudes. A block 40 having an aperture therethrough is keyed to the shaft 39 by means of a key 41. An arm 42 is mounted within the block 40 and carries a knurled or roughened upper portion 43. The knurled portion 43 may be secured to the arm 42 in any suitable manner, such as being threaded thereinto. Yieldable means which preferably comprise a spring 108 is provided for continuously urging the arm 42 in a clockwise direction (Figs. 4 and 5) whereby the knurled portion 43 is caused to engage a lowermost sheet 44 of the pack 36 when the pack is advanced to the position shown in Fig. 4. The arm 42 is yieldably urged in a clockwise direction. with sufiicient force such that the force of the frictional engagement between the knurled portion 43 and the lower sheet 44 is sufficient to peel the leading edge of the sheet 44 from the remainder of the pack 36 as the pack is advanced to left by the pinch rolls 28. As the pack is advanced the arm 42 is pivoted counterclockwise andthe sheet 44 is directed downwardly towards a pair of pinch rolls 45. At some point in the pivotal movement of the arm 42, due to the advance of the sheet 44, the angle between the sheet 44- and the arm 42 becomes sufficiently acute so that the sheet 44 will tend to snap upwardly. A guide 46 suitably secured to the side walls 37 is provided for preventing the sheet 44 from moving upwardly back into engagement with the remainder of the pack 36.

The pinch rolls comprise a power driven roller 47 and a spring pressed pressure roller 48 continuously urged toward the roller 47 by means of a compression spring 49. Both of the rollers 47 and 48 are mounted within the stripping devices in a manner such that the sheet 44 passes therebetween and perpendicularly intersects the plane passing through the axes of both of the rollers, thereby enabling the pinch rolls 45 to advance the sheet 44 towards the conveyor 13 without imparting any bend to the sheet.

A supporting beam 51 rigidly secured to each of the side walls 37 is provided for supporting the remainder of the pack 36 as it leaves the stripping device 11. A plurality of deflectors 52 are mounted on the top of the beam 51 and extend slightly downwardly over the pressure roller 48. As a pack 36 is advanced by means of the pinch rolls 28 until the leading edge thereof is approximately midway through the stripping device 11, the weight of the pack is suflicient to cause it to be bent downwardly somewhat and the deflectors 52 prevent the pack from striking the pressure rollers 48 and guide it across the-beam 51.

The side walls 37 have a pair of bushings 53 mounted therein and within the bushings 53 a rotatable shaft 54 is mounted. Rotatably mounted on the shaft 54 is a pair of housings 55 each of which has a sleeve portion 56. A shaft 57, rotatably mounted within each of the sleeves 56, has a bevel gear .58 rigidly secured thereto which meshes with a bevel gear 59 secured to the shaft 54.

Each of theshafts 57 has an eccentric shaft 60 secured to theend thereof. A collar 61 rotatably mounted on the eccentric shaft 60 has a-race 62 for receiving ball ts bearings 63. A cylindrical ring 64 provided with an inner race within which the ball bearings 63 travel is mounted within a collar 65 secured to a knife 66. When the shafts 57 are rotated the eccentrics impart a reciprocatory motion to the knife 66. A motor 67 suitably mounted on the left side wall 37 (Fig. 3) drives the shaft 54 through suitable belt and pulley connections indicated generally by reference numeral 68.

Fig. 7 shows the preferred form of the knife 66. As is apparent, the knife 66 is serrated to provide a plurality of projections 66a and each of the projections 66a is slotted transversely, as at 66b, to receive one of the circular discs 66c pivotally mounted in the projections at 66d. The periphery of each of the discs 660 is sharpened to a knife edge.

The knife 66, when not being used to strip a sheet from the pack 36, is retained in the position shown in Fig. 4. Each of the housings 55 has a projection 69 which is pivotally connected to a link 70 of a toggle 71. The link 70 is also pivotally secured to a shaft 72 which shaft is pivotally connected to a pair of links 73. The links 73 are also pivotally secured to the side walls 37 of the stripping device 11 by bolts 74 in order to provide a reaction point for the toggle 71. A block 75 rotatably mounted on the shaft 72, has an arm 76, preferably threaded threinto, which extends into a cylinder 77 and carries a piston 78 reciprocable within the cylinder 77. The cylinder 77 is secured to and mounted within a collar 79 which itself is secured to a pair of shafts 80 rotatably mounted in a pair of supports 81 secured to the side walls 37 of the stripping device 11. The cylinder 77 has a pair of apertures 82 and 83 at either end thereof through which fluid may be forced into the cylinder in order to move the piston 78. When fluid is forced into the cylinder 77 through the aperture 82 the piston 7 3 is moved upwardly to thereby break the toggle 71. When the toggle 71 is broken, the knife 66 occupies its inoperative position shown in Fig. 4. When fluid is forced into the cylinder 77, through the aperture 83 the toggle 71 is straightened and the knife 66 is thereby moved to the position shown in Fig. 5.

A control device 84 is mounted suitably in the stripping device 11 and has an arm 85 pivotally mounted therein which carries a sensing disc 86 for sensing the pack 36. if the pack 36 does not extend over the beam 51 the sensing disc 86 occupies the position thereof as shown in Fig. 4, and when the pack 36 lies over the beam 51 the sensing disc 86 is raised slightly whereby the arm 85 is pivoted slightly clockwise in the control device 84, as shown in Fig. 5.

A second control device 87 has an arm 88 pivotally mounted therein, the arm 88 carrying a rotatable disc 89. The arm 88 may be moved downwardly slightly from the position shown in Figs. 4 or and is so moved by means of a stud 98, which protrudes from an arm 91 secured to the shaft 39 whenever the shaft 39 is pivoted counterclockwise due to such movement thereof when the sheet 44 moves the arm 42 counterclockwise.

A block member 92 is secured to the shaft 39 by means of a key 93 and has an arm 94 extending upwardly therefrom. The arm 94 and block 92 may be integrally formed or the arm 94 may be threaded into the block 92. The block 92 is hollow in its lower portion as at 95 and a block 96 is slidable therein. A compression spring 97 urges the block 96 downwardly, whereby a roller 98, rotatably secured to the block 96, cooperates with a plate 99 secured to the side wall 37. The yieldable means which urges the arm 42 towards the pinch rolls 28 causes the shaft 39 to be urged in a counterclockwise direction (Fig. 6) and when the shaft 39 is rotated such that the arm 42 occupies the position shown in Fig. 5, the arm 94 occupies the positon designated by the dot and dash line 100 (Fig. 6) and under these conditions the roller 98 engages a cam surface 161 on the plate 99. When the roller 98 engages the cam surface 101, it acts as a detent to retain the arm 94 in the position designated by the dot and dash line 168 and in'this position the arm 42 occupies the positions shown in Fig. 5. The shaft 39 is retained in this position until the sheet 44 is completely stripped from the remainder of the pack 36 so that the yieldable means is ineffective to move the arm 42 and force the friction surface 43 against the bottom of the sheet 44.

In order to return the arm 42 to its initial position for engaging the lowermost sheet 44 of the pack 36,a fluid operated piston 162 is provided. The piston 102 is reciprocable in a cylinder 163 suitably bolted to the side wall 37. The piston 182 has an operating arm 104 with an enlarged end portion 105 which strikes the arm 94 with a force sufficient to overcome the detent comprising the roller 98 and cam surface 101 when the piston 182 is forced to the left by fluid entering the cylinder 183 through an aperture 106 therein.

In the operation of the present sheet stripping apparatus, the pack of sheets is first moved between the rotatable devices 19 and 26 wherein the pack is flexed to partially separate the different sheets therein prior to moving the pack through the different stripping devices 11. After the pack is thus partially separated, it is moved between the pinch rollers 28 until the lowermost sheet 44 of the pack engages the knurled surfaces 43 on the arm 42. The yieldable means which continuously urges the arm 42 in a clockwise direction (as viewed in Figs. 4 and 5) causes the knurled surface to frictionally adhere to the lower sheet 44. As the pack 36 is advanced due to the adherence between the sheet 44 and the knurled surface 43, the arm 42 is pivoted counterclockwise and in so moving, peels the sheet 44 from the pack 36. The knuried surface 43 remains engaged with the sheet 44 until some time after the leading edge of the sheet 44 passes beneath the guide 46. Thereafter due to the fact that the angle between the sheet 44 and the knurled surface 43 becomes somewhat less than 90 degrees, the sheet 44 will snap upwardly until it engages the guide 46. As the pack 36 and sheet 44 are moved to the left further by the pinch rolls 28, the sheet 44 will eventually engage the upper roller 48 of the pinch rolls 45. The upper roller 48 rotates clockwise and as the sheet 44 is advanced to the left further, it is directed between the two rollers 48 and 47.

When the sheet 44 has advanced to a point somewhere between the guide 46 and the pinch rolls 45, the arm 91 is pivoted counterclockwise sufficiently to cause the stud 90 on the arm 91 to engage the roller 89 and pivot the arm 88 clockwise slightly. When the arm 88 is pivoted clockwise in this manner, suitable means, which may include an electrical relay and associated circuits, are actuated to thereby open a valve connected with the aperture 83 in the cylinder 77 to cause fluid to be forced into the cylinder 77 above the piston 78. The piston 78 is thereby forced downwardly in order to straighten the toggle 71 which causes the knife 66 to be moved to the position in which it is shown in Fig. 5, between the pack 36 and the peeled leading end of the sheet 44. The motor 67, which rotates continuously, causes the knife 66 to be reciprocated due to the action of the eccentric shafts 60, and as the pinch rolls 28 subsequently advance the pack 36 the reciprocating knife 66 and the knife like discs 66c function to completely strip the sheet 44 from the pack 36. By the time that the pack 36 passes through the pinch rolls 28, a corresponding set of pinch rolls 28 in the next successive stripping device 11 will have received the remainder of the pack 36 in order to completely advance it through the next stripping device.

The arms 42 and the knife 66 remain in the positions thereof as shown in Fig. 5 until the entire pack 36 passes beneath the sensing disc 86. When the sensing disc 86 no longer senses the pack 36, the arm pivots counterclockwise to the position shown in Fig. 4 and in so pivoting actuates suitable mechanism for opening a valve connected with the aperture 82 in the cylinder 77. Fluid is thereby caused to enter the cylinder 77 beneath the piston 78 in order to raise the piston to thereby break the toggle 71 and'return the knife 66 to the position shown in Fig. 4. Suitable means are provided which are rendered operable when an arm 107, secured to the toggle link 73, reaches the position thereof as shown inFig. 4, for opening a valve in a fluid circuit connected with the cylinder 163 by means of the aperture 166. When this valve is opened fluid is forced into the cylinder 103 and moves the piston 182 to the left such that the enlarged portion 105 on the arm 104 engages the arm 94 and moves it counterclockwise sufficiently to overcome the detent comprising the roller 98 and cam surface 101. When the roller 98 passes over the peak of the cam surface 191 the compression spring 97 causes the block 96 to be urged downwardly and as the roller 98'rolls over the plate 99, the shaft 39 and arms 42 are returned to their positions as shown in Fig. 4. The stripping device is then ready to operate on the next succeeding pack 36 to be advanced therethrough.

Only a single one of the stripping devices 11 has been described, it being understood that all of them are substantially alike and function in the same manner to strip the lowermost sheet from the pack as it is advanced through each of the stripping devices.

No specific control means have been shown for con trolling the flow of fluid into the various cylinders by reason of the fact that such control means may assume any one of a variety of suitable forms.

It is contemplated that numerous changes and modification may be made in the invention without departing frorn'the spirit or scope thereof.

We claim:

1. In a sheet pack opener, the combination of means for advancinga pack of sheets substantially along a horizontal plane, means for engaging the lowermost sheet in said pack and effective upon the advance of the pack for directing said lowermost sheet downwardly, a knife, and means for moving said knife into a position to further separate said lowermost sheet from said pack upon the subsequent advance of said pack by said advancing means.

2. In a sheet pack opener, the combination of means for advancing a pack of sheets, a pivotable serrated member'for engaging a leading edge of the outer sheet in said pack, means urging said serrated member into engagement with said outer sheet to thereby retain said outer sheet and said serrated member engaged, and a knife, said urging means yielding and said serrated member pivoting on the advance of said pack whereby said outer sheet is directed such that said knife completes the separation of said outer sheet from said. packduring the subsequent advance of said pack past said knife.

3. In an apparatus for separating a pack of. sheets, the combination of-pinch rolls for advancing the pack,'friction'engaging means for separating a leading edge of an outer sheet of the pack from the remainder of said pack during an initial advance of said pack by said pinch rolls, a knife, means controlled by said friction engaging means for moving said knife toward said pinch rolls between the separated leading edge of said outer sheet and said remainder of said pack, and means for reciprocating said knife transversely relative to said pack, whereby said knife functions during subsequent advance of said pack by said pinch rolls for completely separating said outer sheet from said pack.

4. In a sheet pack separating mechanism, the combination of means for advancing a'pack of sheets, a'pivotally mounted arm having a friction surface for engaging a leading end of an outer sheet of said pack and effective upon the advance of said pack to direct the leading end of the outer sheet away from said pack, a control device, a knife, means actuated by said control device for moving said knife to a position between the leading end of said outer sheet and the remainder of said pack, means carried by said .arm and effective upon pivotal movement thereof to a predetermined point by said outer sheet for actuating said control device, and means for reciprocating said knife, whereby said knife functions during subsequent advance of said pack for completely separating said outer sheet from said pack.

5. In a sheet pack opener, the combination of means for advancing a pack of sheets, a conveyor, a second advancing means, a pivotal member for engaging an outer sheet of said pack and effective during the advance of said pack for directing the outer sheet toward said second advancing means, a knife, means for moving said knife to a position between said outer sheet and the remainder of said pack, and means for reciprocating said knife, said reciprocating knife being effective during advance of the pack by said first advancing means to completely sever said outer sheet from the remainder of said pack, said second advancing means being effective upon the severance of said outer sheet from the remainder of the pack for advancing the severed outer sheet toward said conveyor.

6. In a mechanism for opening a pack of sheets the combination of a first means for advancing the pack, a second means for advancing a single sheet from said pack, a pivotal member for frictionally engaging an outer sheet of the pack and effective during the advance of the'pack for peeling the leading edge of the outer sheet from the remainder of the pack and directing it into said second advancing means, a knife, means for moving said knife, and means controlled by said pivotal member and operable upon the pivotal member having completed the directing of said outer sheet into said second advancing means for actuating said knife moving means to cause it to move said knife into a position between the peeled leading edge of the outer sheet and the remainder of said pack, whereby said knife is thereafter effective during the advance of said pack to complete the peeling of said outer sheet from the remainder of said pack and the second advancing means is effective to direct the outer sheet away from the remainder of said pack.

7. In a mechanism for opening a pack of sheets the combination of means for advancing the pack, means for separating a leading edge of one of the sheets from the remainder of the pack, a knife normally maintained in an inoperable position, means for moving said knife into an operable position between the remainder of the pack and said one sheet with its leading edge separated from the remainder of the pack to thereby strip the one sheet from the remainder of the pack, sensing means for sensing the pack during the advance thereof, and means for returning said knife to its first named inoperable position and rendered effective by said sensing means upon the passage of the remainder of the pack past said sensing means.

8. In a mechanism for opening a pack of sheets the combination of means for advancing the pack, means for separating a leading edge of one of the sheets from the remainder of the pack, a knife normally maintained in an inoperable position, means for moving said knife into an operable position between the remainder of the pack and said one sheet with its leading edge separated from the remainder of the pack to thereby strip the one sheet from the remainder of the pack, means controlled by said separating means and effective upon the separation of the leading edge of said one sheet from the remainder of the pack for actuating said moving means, sensing means for sensing the pack during the advance thereof, and means for returning said knife to its first named inoperable position and rendered effective by said'sensing means upon the passage of the remainder of the pack past said sensing means.

9. In a mechanism for opening a pack of sheets the combination of means for advancing the pack, means for separating a leading edge of one of the sheets from the remainder of the pack, said separating means comprising a pivotal member frictionally engaging said leading edge of said one sheet and pivoting during the advance of the pack by said advancing means, a knife normally maintained in an inoperable position, means for moving said knife into an operable position between the remainder of the pack and said one sheet with its leading edge separated from the remainder of the pack to thereby strip the one sheet from the remainder of the pack, means controlled by said pivotal member and effective upon the pivotal movement thereof to a predetermined position for actuating said moving means, sensing means for sensing the pack during the advance thereof, and means for returning said knife to its first named inoperable position and rendered effective by said sensing means upon the passage of the remainder of the pack past said sensing means.

10. In a mechanism for opening a pack of sheets, the combination of means for advancing the pack, means for separating a leading edge of one of the sheets from the remainder of the pack, said separating means comprising a pivotal member for frictionally engaging said leading edge of said one sheet and pivoting during the advance of the pack by said advancing means, a knife normally maintained in an inoperable position, means for moving said knife into an operable position between the remainder of the pack and said one sheet with its leading edge separated from the remainder of the pack to thereby strip the one sheet from the remainder of the pack, means controlled by said pivotal member and effective upon the pivotal movement thereof to a predetermined position for actuating said moving means, sensing means for sensing the pack during the advance thereof, means for returning said knife to its first named inoperable position and rendered effective by said sensing means upon the passage of the remainder of the pack past said sensing means, and means rendered effective upon the return of said knife to its first named inoperable position for returning said pivotal member from said predetermined position to a position in which it can engage a leading edge of one of the sheets in the next succeeding pack advanced by said advancing means.

11. In a mechanism for opening a pack of sheets, the combination of means for advancing the pack, means for separating a leading edge of one of the sheets from the remainder of the pack, said separating means comprising a pivotal member for frictionally engaging said leading edge of said one sheet and pivoting during the advance of the pack by said advancing means, a knife normally maintained in an inoperable position, means for moving said knife into an operable position between the remainder of the pack and said one sheet with its leading edge separated from the remainder of the pack to thereby strip the one sheet from the remainder of the pack, means controlled by said pivotal member and effective upon the pivotal movement thereof to a predetermined position for actuating said moving means, sensing means for sensing the pack during the advance thereof, and means for returning said knife to its first named inoperable position and rendered effective by said sensing means upon the passage of the remainder of the pack past said sensing means, a detent for retaining said pivotal member in said predetermined position, and means rendered effective upon the return of said knife to its first named inoperable position for rendering said detent ineffective to retain said pivotal member and returning said pivotal member from said predetermined position to a position in which it can engage a leading edge of one of the sheets in the next succeeding pack advanced by said advancing means.

12. In a sheet pack opener, the combination of means for advancing a pack of sheets substantially along a horizontal plane, means for engaging the lowermost sheet in said pack and effective upon the advance of the pack for directing said lowermost sheet downwardly, a knife having a cutting edge comprising a plurality of knife-like rotatable discs, means for moving said knife between said pack and said downwardly directed lowermost sheet, and means for reciprocating said knife to enable said knifelike discs to complete the separation of said lowermost sheet from said pack during subsequent advance of said pack past said knife.

References Cited in the file of this patent UNITED STATES PATENTS 1,207,668 Trood Dec. 5, 1916 1,527,756 Steele Feb. 24, 1925 1,586,607 Carafilidis June 1, 1926 1,790,878 Peterson Feb. 3, 1931 1,923,264 Hinderer Aug. 22, 1933 

